Aspect Ratio Finder

How it works

1. 1Type a width and a height in the left panel "Find the ratio of a size" to see the simplified ratio, the decimal ratio and the shape (landscape, portrait or square).
2. 2Read the line that names the closest common ratio. If it is not exact, the percent difference is shown.
3. 3To measure a picture, choose an image file under "Or read the size of a picture". Its width and height fill the two boxes.
4. 4In the right panel "Find the other side", enter a ratio or pick one of the common ratio buttons.
5. 5Choose Width or Height under "I know the", type a value in pixels, and read the other side in the result.

How to use the Aspect Ratio Finder

The page has two panels. The left panel finds the ratio of a width and height you enter. The right panel finds the other side when you know one side and a ratio.

Both panels update as you type, so you do not need to press a button.

Start with the defaults if you want to see how it works. The left panel opens with 1920 and 1080, and the right panel opens with 16:9 and a width of 1280.

What an aspect ratio is

An aspect ratio is the relationship between the width and the height of a shape. It is written as two numbers, such as 16:9, which means the width is 16 parts for every 9 parts of height.

The same ratio can describe very different sizes. 1920 x 1080 and 1280 x 720 both simplify to 16:9.

The ratio can also be written as a decimal. You get it by dividing the width by the height, so 16:9 is 1.778:1.

• Landscape: wider than it is tall.
• Portrait: taller than it is wide.
• Square: width and height are equal.

How the aspect ratio calculator simplifies a size

To simplify a size, the calculator divides both sides by their greatest common divisor, which is the largest whole number that divides both evenly. The result is the smallest pair of whole numbers with the same proportion.

For example, 1920 x 1080 has a greatest common divisor of 120, so the ratio is 16:9. A square such as 1000 x 1000 simplifies to 1:1, and 1080 x 1920 simplifies to 9:16.

Use the simplified ratio to compare sizes. Two sizes with the same simplified ratio have the same shape, even if their pixel counts differ.

Find the missing side of a ratio

When you know one side and the ratio, you can find the other side with a simple multiplication. For a height, multiply the width by the ratio height and divide by the ratio width. For a width, multiply the height by the ratio width and divide by the ratio height.

For example, a width of 1280 at 16:9 gives a height of 720. A height of 1080 at 4:3 gives a width of 1440.

Ratios with decimals work too. A width of 1000 at 1.91:1 gives a height of 523.56, which rounds to 524 px.

Common aspect ratios

Some ratios appear often in photos, screens and video. The buttons on the right panel include 1:1, 5:4, 4:3, 3:2, 16:10, 16:9, 21:9, 4:5, 3:4, 2:3 and 9:16.

1:1 is a square. 4:3 and 3:2 are common photo and older screen shapes. 16:9 is the common widescreen shape for video and monitors. 21:9 is an ultrawide shape.

9:16 is 16:9 turned to portrait, which gives 1080 x 1920. 4:5 is a tall portrait shape.

Image aspect ratio finder: read the size of a picture

The file chooser under the left panel reads the width and height of a picture. Choose an image file, and its size fills the two boxes. From there, the calculator shows the image aspect ratio in the same way it does for any typed size.

The picture is only measured in your browser. It is not uploaded. If you choose a file that is not an image, the page shows an error message.

Reading the size is useful when you want to know the shape of a photo before you crop it or fit it into a fixed frame.

When a size is not an exact common ratio

Not every size matches a common ratio exactly. For example, 1366 x 768 has a greatest common divisor of 2, so its simplified ratio is 683:384. That is close to 16:9 but not the same.

The line under the result names the closest common ratio. In this case, it is 16:9, and the difference is less than 0.1 percent.

A small difference like this is normal for many screen and camera sizes. The percent shown tells you how far the size is from the common ratio.

Aspect ratio changer: what this page does not do

This page finds the ratio and the missing side. It does not change the aspect ratio of a picture. It does not crop, resize or fill empty space.

To change a picture, use the crop and resize tools on this site. Crop PNG lets you crop a picture to a ratio, and Resize PNG changes the picture size.

If a picture is moved to a different ratio without cropping or adding space, it will look stretched. Check the ratio here first, then change the picture in one of those tools.

Privacy: nothing is uploaded

The calculation runs in your browser. The size you type, the ratio you choose and any picture you open are handled on your device. Nothing is uploaded to a server.

The image size reader only measures the file in your browser. It does not send the picture anywhere.

You can use the calculator without sending any file to the site.

Questions